During hydrocarbon drilling or mining, the gradient acceleration of a mass due to gravity is measured and used to gain information about the density of geological formations below the ground's surface. Measurement of the acceleration of a mass due to the force of gravity is performed by repeatedly dropping the mass and measuring variations of the drop of the mass during freefall. When performing the gravity measurement experiments, forces acting on the mass (force loop) and the forces affecting the instrumentation used to measure the gravity effects (measurement loop) may interact, causing part of the recoil force produced as a reaction to the gravitation force on the mass, to transfer to the measurement instrumentation, thereby resulting in self-induced interference and degradation of the measurement results.
Decoupling the force and measurement loops is a basic pursuit when designing ultra-precision instrumentation. Assuming the force and measurement loops could be completely decoupled, the gauging instruments would have no influence on the experiment and vice versa. However, in practice, absolute decoupling is impracticable and the design objective therefore becomes one of minimizing the self-induced disturbances or interference. For some applications, a measure of self-induced interference is tolerated. However, some experiments require extremely precise measurements and at such minute scale (for example 1 micro-Gal) that the self-induced interference produces noise to signal ratios that prevent the desired signal from being measurable. Certain precision experiments may be carried out in specially designed test platforms that operate in zero gravity environments such as in outer space. While this avoids the need to support the static weight of relevant apparatus, thereby providing an alternative means of decoupling, operating in zero gravity environments is expensive, forcing the experimenter to purchase space on a vehicle (e.g. a satellite, rocket, and/or space station) appropriate for conducting the experiment.
Space limitations are also a factor. The miniaturization of gravimeters requires spatial overlapping force and measurement loops, thereby compounding the difficulty in preventing crosstalk between the loops. Alternate means of reducing parasitic effects of force and measurement loop coupling are desired in an apparatus small enough to be used in drilling, logging, or monitoring operations, such as down hole in a sensor device such as a logging sonde,